1. Field
The present disclosure relates to optical films for reducing color shift and/or organic light-emitting display apparatuses employing the same.
2. Description of the Related Art
An organic light-emitting diode (OLED) includes an anode, an organic light-emitting layer, and a cathode. Here, when a voltage is applied between the anode and the cathode, holes are injected from the anode into the organic light-emitting layer, whereas electrons are injected from the cathode into the organic light-emitting layer. At this point, the holes and electrons injected into the organic light-emitting layer are re-combined and generate excitons, and light is emitted as the excitons transit from an excited state to a ground state.
Because a light-emitting body of such an OLED is an organic material, lifespan deterioration is the core problem regarding the development of OLED, and many techniques are being focused to resolve the problem.
From among the techniques, a technique using a microcavity structure is a technique for increasing an intensity of a light of a particular wavelength by resonating the light and emitting the light of the particular wavelength to outside. In other words, the microcavity structure is a structure in which distances between anodes and cathodes are designed to respectively correspond to representative wavelengths of red (R), green (G), and blue (B), so that only light of wavelengths corresponding thereto resonate and are emitted, and lights of other wavelengths are weakened. As a result, light emitted outside of the structure becomes more intense and sharper, thereby improving brightness and color purity. Furthermore, increased brightness causes reduced power consumption, thereby inducing increased lifespan.
However, in a microcavity structure, wavelengths to be amplified are determined based on a thickness of an organic deposition material layer. Here, a length of a light path changes at lateral sides, thereby causing an effect similar to a change in the thickness of an organic deposition material layer. Therefore, the wavelengths to be amplified are changed.
In other words, as the viewing angle is tilted from the front to a side, the maximum resolution wavelength becomes shorter, and thus a color shift occurs as the maximum resolution wavelength decreases. For example, even if white color is embodied at the front, the white color may become bluish at a lateral side due to blue shift phenomenon.